Fluid-pressure and analogous brake systems – Multiple systems – Fluid pressure and electric
Patent
1998-02-05
2000-06-27
Schwartz, Christopher P.
Fluid-pressure and analogous brake systems
Multiple systems
Fluid pressure and electric
303 975, 303123, 3031192, 13762564, 13762565, 25172903, B60T 1374
Patent
active
060797908
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF THE INVENTION
This invention relates to a brake system for a trailer vehicle comprising, provided on the trailer vehicle, a trailer fluid pressure supply system comprising a reservoir and a coupling connectable to a fluid pressure outlet of a tractor vehicle, transducer means responsive to a fluid pressure brake demand signal, delivered to the transducer means from a further coupling connectable to a fluid pressure brake demand signal outlet of the tractor vehicle, to provide an electrical brake demand signal; electronic control means responsive to the electrical brake demand signal to provide an electrical brake operating signal; a brake valve means responsive to said electrical brake operating signal for brake application; said brake valve means comprising a supply valve means and an electrically operable valve means having an inlet and an outlet and responsive to said electrical brake operating signal to provide, at said electrically operable valve outlet, a fluid pressure brake operating signal which is dependent on said fluid pressure brake demand signal; means to connect said electrically operable valve outlet to a fluid pressure brake operating signal inlet of the supply valve means and said supply valve means being responsive to said fluid pressure brake operating signal to supply fluid from said source to at least one actuator for brake application under a brake pressure controlled by said supply valve means in accordance with the said received fluid pressure brake operating signal and an electrically operable demand signal control valve responsive to presence or absence of electrical supply to said system respectively to prevent or to permit delivery of said fluid pressure brake demand signal to the supply valve means to provide an alternative fluid pressure brake operating signal for the supply valve means, and a pressure responsive emergency valve to connect said reservoir to the supply valve means to provide an alternative fluid pressure brake operating signal therefor when the pressure in the supply to said reservoir falls below a predetermined value. Such a brake system is referred to hereinafter as being of the kind specified.
In such a brake system the electrically operable demand signal control valve is provided as a discrete valve separate from the pressure responsive emergency valve. Accordingly, the system is relatively complex and expensive to produce.
An object of the invention is to provide a brake system of the kind specified which is less complex and more economical to produce.
According to one aspect of the present invention we provide a brake system of the kind specified having a combined electrically operable demand signal control valve and emergency valve comprising a first inlet connected to the supply line, a second inlet connected to the reservoir, and an outlet connectable to the fluid pressure brake operating signal inlet of the supply valve means, a valve member to control flow of fluid pressure between the second inlet and the outlet and said valve member being movable by electrical means responsive to said presence or absence of electrical supply to the system and by fluid pressure means responsive to said pressure in the supply falling below said predetermined value.
The combined valve may have a third inlet to which the fluid pressure brake demand signal is supplied and the outlet may be connectable to the fluid pressure brake operating signal inlet of the supply valve means.
Alternatively, the outlet of the combined valve may be connected to one inlet of a selector valve which has a second inlet to which the fluid pressure brake demand signal is supplied and an outlet connected to the fluid pressure brake operating signal inlet of the supply valve means and means to select between connection of the first inlet or the second inlet to the outlet according to the pressure difference between the first and second inlets.
The valve member may be moveable between a first position in which it prevents flow between the second inlet and the outlet and a second
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A.Schmitt: "Der Hydraulik Trainer", pp. 4,104,105, G.L. Rexroth GmbH, 1981.
Haldex Brake Products Limited
Schwartz Christopher P.
Williams Thomas J.
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